Smoking can cause changes in several genes, increasing the risk of developing cancer and diabetes, a new study has found.

Researchers from Uppsala University and Uppsala Clinical Research Center in Sweden found that smoking affects genes which increase the risk for cancer and diabetes, or are important for the immune response or sperm quality.

They examined how the genes are changed in smokers and users of non-smoke tobacco.

The study identified a large number of genes that were altered in smokers but found no such effect of non-smoke tobacco.

"This means that the epigenetic modifications are likely not caused by substances in the tobacco, but by the hundreds of different elements that are formed when the tobacco is burnt," said Asa Johansson, researcher at the Department of Immunology, Genetics and Pathology at Uppsala University and Uppsala Clinical Research Center, who led the study.

"Our results therefore indicate that the increased disease risk associated with smoking is partly a caused by epigenetic changes.

"A better understanding of the molecular mechanism behind diseases and reduced body function might lead to improved drugs and therapies in the future," said Johansson.

It has been previously known that smokers have an increased risk of developing diabetes and many types of cancer, and have a reduced immune defence and lower sperm quality.